RF Front-End Filter Bypass for AGC-Based Sensitivity Control
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Solution Overview
Problem
Radio frequency communication systems face insertion loss and degraded receive sensitivity due to filters used for blocker filtering, which also introduce power amplifier output power increases and coexistence issues in transmit chains, and linearity and susceptibility penalties in receive chains.
Innovation Solution
Implementing a front-end system with a transceiver that can dynamically change filter connectivity and gain settings based on automatic gain control, allowing for filter bypass modes to enhance receive sensitivity and reduce transmit path insertion loss, using tunable filters and low noise amplifiers with adjustable bias and gain, and employing time or frequency division duplexing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If filters are used for blocker filtering in the front-end system, then blocker rejection is improved, but receive sensitivity is degraded due to insertion loss
Solution Approach 1:
The patent implements dynamic filter bypass capability that allows the front-end system to switch between filtered and unfiltered signal paths based on operating conditions. The transceiver can selectively activate bypass paths to circumvent filters when receive sensitivity is critical, and engage filters when blocker rejection is needed, making the system adaptable to varying signal environments.
Solution Approach 2:
The system changes the connectivity parameter of the filter by introducing controllable switches that can alter the signal path. By dynamically adjusting the filter's presence in the signal chain through electronic switching, the system optimizes between blocker rejection and receive sensitivity based on current operating requirements.
2Object-affected harmful factors
If filters are used for blocker filtering, then blocker rejection is improved, but transmit path insertion loss increases
Solution Approach 1:
The transmit path incorporates dynamic bypass switches that allow the system to selectively engage or disengage filters based on transmission requirements. When power efficiency is prioritized and blocker conditions are manageable, the bypass path eliminates filter insertion loss. When spectral masking or blocker rejection is needed during transmission, the filters are activated.
3Object-affected harmful factors
If filters are used for blocker filtering, then blocker rejection is improved, but device complexity increases
Solution Approach 1:
The bypass switches and control logic are integrated into the existing front-end architecture, allowing the same switching mechanism to serve multiple functions: receive path bypass, transmit path bypass, and dynamic reconfiguration. This multi-functionality reduces the need for separate dedicated components for each bypass function, thereby limiting the increase in overall system complexity.
4Reliability
If filter bypass is implemented to reduce insertion loss, then receive sensitivity is improved, but blocker susceptibility increases
Solution Approach 1:
The system incorporates blocker detection feedback mechanisms that monitor the signal environment and automatically control the bypass switches. When strong blockers are detected, the feedback signal activates the filter to provide protection. When the environment is clean, the bypass is enabled to maximize sensitivity, creating a closed-loop system that adaptively manages the trade-off between sensitivity and blocker susceptibility.
Data Source
AI summary
Apparatus and methods for filter bypass for radio frequency front-ends are provided. In certain configurations, filter connectivity of a front-end is changed as a function of automatic gain control (AGC) in a receive path. For example, lossy filtering can be bypassed when signal conditions and the surrounding interference environment allow. In certain implementations, an additional gain state is added to the AGC in the form of a bypass of the filtering. Thus, receiver gain and noise figure are greatly improved while the linearity and susceptibility to blockers is degraded.